ggml-cpu/x86: fix unused changemask warning in repack (#20692) #8

Job	Run time
openEuler-latest-cann (x86, 910b, Release, on)	14m 35s
openEuler-latest-cann (aarch64, 910b, Release, off)	9m 53s
openEuler-latest-cann (aarch64, 910b, Release, on)	10m 26s
openEuler-latest-cann (x86, 310p, Release, off)	12m 35s
openEuler-latest-cann (x86, 910b, Release, off)	10m 36s
openEuler-latest-cann (aarch64, 310p, Release, off)	8m 59s
	1h 7m 4s

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